My U.S. Pat. No. 3,921,656 discloses self-closing breakaway valve assemblies of the type comprising two valve housings joined by a frangible connecting means, each valve housing having mounted therein a rotatable valve member which is spring-biased to close. Trigger means in the form of spider members spanning bores of the rotatable valve members and a trigger ball captured between the spider members maintains the rotatable valve members in their open position, with flow through aligned bores, until separation of the housings. Upon separation of the housings, the trigger ball providing engagement between the spider members is released, and the rotatable valve members rotate to their closed position.
Self-closing breakaway valve assemblies are installed in the fuel lines of aircraft or other vehicles in positions where the fuel line is vulnerable to being severed in a crash. Absent a self-closing breakaway valve assembly, a severed fuel line would permit fuel contained within the fuel line and the fuel tanks connected thereto to escape and cause or contribute to a fire.
A major advantage in this self-closing breakaway valve assembly is the central location of the trigger ball, wherein valve closure is initiated evenly without any dependence upon the particular location of housing separation.
A first concern with the self-closing breakaway valve assemblies generally described above is that the trigger ball could become lodged with one of the spider members, such as by corrosion or the like. This problem was addressed in my U.S. Pat. No. 4,295,484, in which bevelled surfaces are provided to "kick-out" the trigger ball in the event it is carried by one of the spider members when the valve members are rotating to the closed position. This "kick-out" provision is sufficient unless the ball is securely affixed to the spider member, but has the disadvantage of requiring extra structure, space and complexity.
A second concern with the loose trigger ball is the possibility that it could become wedged in either the self-closing breakaway valve assembly or in any other mechanisms employed in the safe vicinity. A third concern with the loose trigger ball is the additional difficulty it presents in assemblying the self-closing breakaway valve assemblies, in that the free trigger ball may become dislodged before proper engagement of the spider members is achieved.